Measuring some 50 feet (15 meters) in length, the bone-crunching predator represents one of the largest marine reptiles ever known, according to a team led by Jørn Hurum of the Natural History Museum in Oslo, Norway.

The 150-million-year-old creature was first discovered in 2006 on Spitsbergen, part of Norway's Svalbard archipelago, in a polar wasteland littered with fossilized sea reptiles (see map).

"We knew immediately this was something special," Hurum said. "The large pieces of bone and the structure of the fragments told us that this was big."

Hurum's team returned last summer to the Arctic island to excavate the fossil.

Removing a hundred tons of rock by hand while watching out for polar bears, the team recovered a large chunk of the skeleton, including portions of its estimated ten-foot-long (three-meter) skull, an almost complete forelimb, and sections of its dinner-plate-size vertebrae.

Dubbed "the Monster," it's thought to be a previously unknown species of plesiosaur.

"It's as big or bigger than the largest plesiosaur ever found," Hurum said. "This absolutely looks like a new species," he added.

Plesiosaurs were marine reptiles that typically had small heads, long necks, and large flippers.

But the newfound plesiosaur is thought to have been a pliosaur, and pliosaurs were different from other plesiosaurs.

With short necks and massive heads, pliosaurs became the top marine predators during the Jurassic period, 200 to 145 million years ago.

Hurum said the newly excavated specimen is 20 percent bigger than what was until now the largest known pliosaur, Kronosaurus from Australia.

Calling the latest find "the T. rex of the ocean," Hurum said it "would have eaten other marine reptiles and maybe some of the huge bony fishes that were around at that time."

The newly excavated pliosaur was unveiled today at the Natural History Museum in Oslo.

Patrick Druckenmiller, a plesiosaur expert at the University of Alaska's Museum of the North, was a member of the expedition team that found and excavated the Arctic fossil.

"Not only is this specimen significant in that it is one of the largest and relatively complete plesiosaurs ever found, it also demonstrates that these gigantic animals inhabited the northern seas of our planet during the age of dinosaurs," Druckenmiller commented.

"Although we didn't get the entire skeleton, we found many of the most important parts," Druckenmiller said. "Amazingly, the paddle [of its forelimb] alone is nearly ten feet [three meters] long."

The fossil was found in permafrost among a prehistoric "graveyard" of large marine reptiles approximately 800 miles (1,300 kilometers) from the North Pole.